Correlation between Retinal Morphological Development and Development of the Electroretinogram in the Dog
College of Veterinary Medicine, Michigan State University, USA G355, Veterinary Medical Center, Michigan State University
East Lansing, MI, USA
This study was performed to compare the morphological maturation of the retina with its functional maturation in dogs.
Materials & Methods
A scotopic intensity series electroretinogram was recorded weekly following eyelid opening from seven dogs. For retinal morphology, tissues were fixed, plastic embedded and sections taken in a vertical plane through the optic nerve head. The thickness of retinal layers was measured at 8 regions across the retina using Neurolucida software (MicroBrightField).
At 2 weeks of age, the peripheral retina was thicker than the central retina. The photoreceptor inner segments were present and a low amplitude ERG could be recorded. By 4 weeks of age the photoreceptor outer segments had formed but were not fully developed. The photoreceptor cell layer reached maximal thickness at approximately 7 week of age at which time maximal ERG responses were recorded. The photoreceptor cell layer became thinner by 16 weeks of age and this was reflected by a decrease in ERG amplitudes.
The ERG amplitudes correlate with the photoreceptor cell layer thickness. ERG achieves adult waveform as photoreceptor cell layer achieves maximal thickness.